Rotate camera on mouse drag, minor glitch

I have a script I modified from the standard scripts mouseOrbit library. I have a scene and I just want people to be able to click and hold the left mouse button and while holding, drag to rotate the camera. It pretty much works exactly as it should except one minor issue. The very first time the scene loads, whenever I left click in the scene the camera rotation jumps noticeably to the right. Thereafter it works as expected, and only repositions if I click, hold and drag. But for some reason the first time I single click it jumps. Would appreciate someone's suggestion on what might be happening.

Here's the modified script. It should be pretty straight forward. It stores the x and y angle of rotation on startup, then on late update whenever the mouse is held down it gets the change in x and y axis and rotates based off that changed value.

Appreciate the help in advance!

 var xSpeed = 250.0;
 var ySpeed = 120.0;
 
 var yMinLimit = -20;
 var yMaxLimit = 80;
 
 var xMinLimit = -20;
 var xMaxLimit = 80;
 
 private var x = 0.0;
 private var y = 0.0;
 
 @script AddComponentMenu("Camera-Control/Mouse Orbit")
 
 function Start () {    
 
     var angles = gameObject.transform.eulerAngles;
     y = transform.rotation.y;
     x = transform.rotation.x;
 
     // Make the rigid body not change rotation
     if (GetComponent.<Rigidbody>())
         GetComponent.<Rigidbody>().freezeRotation = true;
 }
 
 function LateUpdate () {
 
     if (Input.GetMouseButton(0)) {
 
         x += Input.GetAxis("Mouse X") * xSpeed * 0.02;
         y -= Input.GetAxis("Mouse Y") * ySpeed * 0.02;
         
         y = ClampAngle(y, yMinLimit, yMaxLimit);
         x = ClampAngle(x, xMinLimit, xMaxLimit);
 
         var rotation = Quaternion.Euler(y, x, 0);
         
         transform.rotation = rotation;
     }
 }
 
 static function ClampAngle (angle : float, min : float, max : float) {
     if (angle < -360)
         angle += 360;
     if (angle > 360)
         angle -= 360;
     return Mathf.Clamp (angle, min, max);
 }